1. Field of the Invention
The present invention relates to an optical recording method and apparatus that records information onto an optical storage medium at a high speed by emitting a light beam to a recording layer of the storage medium. Further, the present invention relates to an optical storage medium that stores information recorded by using the optical recording method and apparatus.
2. Description of the Related Art
Recently, optical storage media, including CD-R (compact disk recordable), CD-RW (compact disk rewritable) and so on, become widespread. Each storage medium is provided for recording information thereon by focusing a light beam onto a recording layer of the medium and changing the phase of the recording layer material.
As disclosed in Japanese Laid-Open Patent Application No. 63-29336, an optical recording method that records information onto a recording layer of an optical recording medium by emitting light to the recording layer of the medium is known. In the optical recording method of the above document, a light source driving waveform is applied to a light source to control emission of a light beam to the recording layer of the medium based on a write data modulation method. Moreover, there is known an optical recording method that determines an optimum light source driving waveform (including the write power and the write pulse width), which is applied to the light source, based on a readout signal of the recorded information derived from a reflection light beam from the optical disk.
Further, several optical recording methods have been proposed for improvement of the quality of the write signal recorded on a rewritable phase-change storage medium. For example, Japanese Laid-Open Patent Application No. 63-266632 discloses such improvement method. In the conventional method of the above document, a pulse width modulation (PWM) method is utilized for application of a multi-pulse light source driving waveform to the light source to control emission of a light beam from the light source to a rewritable phase-change optical disk having a recording layer with a large crystallization speed. The conventional method provides the driving waveform that is effective in recording a long amorphous mark on the recording layer of the optical disk.
In addition, Japanese Laid-Open Patent Application No. 63-266633 and U.S. Pat. No. 5,150,352 disclose an optical recording method which eliminates positional variations of a mark edge and improves the jitter characteristics of an optical disk by applying a driving waveform including a front-end portion or a tail-end portion having an increased pulse width or with an increased power level to the light source.
Further, the rewritable compact disk standards (the orange book, part III, ver. 2.0) provide the recommended specifications of 1xc3x97 to 4xc3x97 linear velocity recording of the rewritable recording media. The linear velocities 1xc3x97 to 4xc3x97 according to the standards (the orange book, part III, ver. 2.0) range from 1.2 m/s to 5.6 m/s. The recording speeds of the media in this range require a relatively long time to record information onto the media. There is an increasing demand for a reliable CD-RW drive that is able to carry out error-free information recording with good write-erase characteristics at higher recording speeds. Preparations of high-speed specifications of 4xc3x97 to 10xc3x97 linear velocity recording for the rewritable compact disk standards are now under way. The linear velocities 4xc3x97 to 10xc3x97 according to the standards (the orange book, part III) range from 5 m/s to 28 m/s.
Accordingly, it is desirable to provide an optical recording method and apparatus that ensures good write/erase characteristics of the rewritable phase-change medium and retains the compatibility with the write-once storage medium when high-speed recording (equivalent to the 4xc3x97 to 10xc3x97 linear velocity recording) is performed. The conventional recording methods and devices of the above documents are not yet adequate to attain the goal.
It is a general object of the present invention to provide an optical recording method and apparatus in which the aforementioned problems are eliminated.
Another object of the present invention is to provide an optical recording method and apparatus that ensures good write/erase characteristics of the rewritable phase-change medium and retains the compatibility with the write-once storage medium when high-speed recording is performed.
Another object of the present invention is to provide an optical recording method and apparatus that provides increases of initial characteristics and overwrite performance of the rewritable phase-change medium.
Another object of the present invention is to provide an optical storage medium that stores information recorded by using the optical recording method and apparatus such that good write/erase characteristics of the rewritable phase-change medium are ensured and the compatibility with the write-once storage medium is retained when high-speed recording is performed.
The above-mentioned objects of the present invention are achieved by an optical recording method which records a sequence of data blocks onto a recording layer of an optical recording medium by emitting light to the recording layer of the medium and changing a phase of a recording material of the recording layer, the method comprising the steps of: applying a light source driving power to a light source to control emission of a light beam to the recording layer of the medium, the driving power including a sequence of mark and space portions, each mark potion having a pulse width that corresponds to a multiple of a period T of a write clock based on a write data modulation method; setting a multi-pulse waveform of each mark portion of the driving power that includes a front-end portion, a multi-pulse portion and a tail-end portion, the front-end portion having a first pulse width t1 with a high-power write level Pw and starting from a middle-power erase level Pe, the multi-pulse portion including a sequence of write pulses each having a second pulse width t2 with the write level Pw and a third pulse width t3 with a low-power base level Pb, the multi-pulse portion having a given duty ratio z=t2/(t2+t3), and the tail-end portion having a fourth pulse width t4 with the base level Pb and ending at the erase level Pe; setting a linear velocity of rotation of the medium at a controlled speed; and controlling the waveform when the linear velocity of rotation of the medium is set in a high-speed range from 5 m/s to 28 m/s, such that the first pulse width t1 of the front-end portion ranges 0.1T to 1T and the fourth pulse width t4 of the tail-end portion ranges 0.2T to 1.3T.
The above-mentioned objects of the present invention are achieved by an optical recording apparatus which records a sequence of data blocks onto a recording layer of an optical recording medium by emitting light to the recording layer of the medium and changing a phase of a recording material of the recording layer, the apparatus comprising: a light source driver unit which applies a light source driving power to a light source to control emission of a light beam to the recording layer of the medium, the driving power including a sequence of mark and space portions, each mark potion having a pulse width that corresponds to a multiple of a period T of a write clock based on a write data modulation method; a write power determination unit which sets a multi-pulse waveform of each mark portion of the driving power that includes a front-end portion, a multi-pulse portion and a tail-end portion, the front-end portion having a first pulse width t1 with a high-power write level Pw and starting from a middle-power erase level Pe, the multi-pulse portion including a sequence of write pulses each having a second pulse width t2 with the write level Pw and a third pulse width t3 with a low-power base level Pb, the multi-pulse portion having a given duty ratio z=t2/(t2+t3), and the tail-end portion having a fourth pulse width t4 with the base level Pb and ending at the erase level Pe; and a controller which sets a linear velocity of rotation of the medium at a controlled speed, wherein the controller causes the write power determination unit to control the waveform when the linear velocity of rotation of the medium is set in a high-speed range from 5 m/s to 28 m/s, such that the first pulse width t1 of the front-end portion ranges 0.1T to 1T and the fourth pulse width t4 of the tail-end portion ranges 0.2T to 1.3T.
The above-mentioned objects of the present invention are achieved by an optical storage medium which stores information recorded by using an optical recording method that records a sequence of data blocks onto a recording layer of an optical recording medium by emitting light to the recording layer of the medium and changing a phase of a recording material of the recording layer, the optical recording method comprising the steps of: applying a light source driving power to a light source to control emission of a light beam to the recording layer of the medium, the driving power including a sequence of mark and space portions, each mark potion having a pulse width that corresponds to a multiple of a period T of a write clock based on a write data modulation method; setting a multi-pulse waveform of each mark portion of the waveform that includes a front-end portion, a multi-pulse portion and a tail-end portion, the front-end portion having a first pulse width t1 with a high-power write level Pw and starting from a middle-power erase level Pe, the multi-pulse portion including a sequence of write pulses each having a second pulse width t2 with the write level Pw and a third pulse width t3 with a low-power base level Pb, the multi-pulse portion having a given duty ratio z=t2/(t2 +t3), and the tail-end portion having a fourth pulse width t4 with the base level Pb and ending at the erase level Pe; setting a linear velocity of rotation of the medium at a controlled speed; and controlling the waveform when the linear velocity of rotation of the medium is set in a high-speed range from 5 m/s to 28 m/s, such that the first pulse width t1 of the front-end portion ranges 0.1T to 1T and the fourth pulse width t4 of the tail-end portion ranges 0.2T to 1.3T, the optical storage medium comprising the sequence of data blocks recorded on the recording layer, each data block including first information indicative of the first pulse width t1 of the front-end portion and second information indicative of the fourth pulse width t4 of the tail-end portion in the light source driving waveform.
In the optical recording method and apparatus of the present invention, the driving power is applied to the light source to control emission of a light beam to the recording layer of the optical storage medium, the driving power including a sequence of mark and space portions, each mark potion having a pulse width that corresponds to a multiple of the period T of the write clock. The waveform of each mark portion of the driving power includes the front-end portion, the multi-pulse portion and the tail-end portion, the front-end portion having the first pulse width t1 with the write level Pw and starting from the erase level Pe, the multi-pulse portion including the write pulses each having the second pulse width t2 with the write level Pw and the third pulse width t3 with the base level Pb, the multi-pulse portion having the duty ratio z=t2/(t2+t3), and the tail-end portion having the fourth pulse width t4 with the base level Pb and ending at the erase level Pe. The waveform is controlled, when the linear velocity of rotation of the medium is set in a range from 5 m/s to 28 m/s, such that the first pulse width t1 ranges 0.1T to 1T and the fourth pulse width t4 ranges 0.2T to 1.3T. As the front-end edge and the tail-end edge of each mark (the amorphous phase) are accurately and definitely created on the recording layer of the rewritable phase-change medium when high-speed recording is performed, the optical recording method and apparatus of the present invention can ensure good write/erase characteristics of the rewritable phase-change medium and retain the compatibility with the write-once storage medium when high-speed recording is performed. The optical recording method and apparatus of the present invention are effective in increasing the initial characteristics and the overwrite performance of the rewritable phase-change medium.